Double-acting two-stroke internal-combustion engine



Nov. 15, 1949 v M. F. MEINERTZ' 2,438,093

DOUBLE-ACTING TWO-STROKE INTERNAL-COMBUSTION ENGINE Filed May as, 1946 2Sheets-Sheet 2 Inventor H. FMezLzz/epiz Patented Nov. 15, 1949DOUBLE-ACTING TWO-STROKE INTERNAL- COMBUSTION ENGINE Mark FerdinandMeinertz, Copenhagen, Denmark Application May 23, 1946, Serial No.671,774 In Denmark May 17, 1945 Section 1, Public Law 690, August 8,1946 Patent expires May 17, 1965 3 Claims. (Cl. 12361) Double-actingtwo-stroke engines are known with transverse or reverse scavenging atboth cylinder ends. These engines are Simple because the admission andexhaust can be controlled by the working piston alone, for which reasonthere will be a minimum number of movable parts, but on account of theimperfection of the scavenging system they have comparatively small meanpressures and consequently their weight and the space they take up arecomparatively large as compared with the efiect they yield. Furthermorethey are strongly subjected to very unfortunate unequal heat stresses onaccount of the uneven heating of the port sections of the cylinders.

Double-acting two-stroke engines are also known with longitudinalscavenging at both cylinder ends, the scavenging ports being controlledby the working piston while the exhaust occurs through exhaust membersin the form of pistons or slide valves mounted in both cylinder ends.

The application of slide valves necessitates separate drives for thesefrom the crank shaft which entails that the length of the engine andthereby its weight get comparatively large in spite of the high meanpressure made possible by the longitudinal scavenging.

Various constructions of double-acting twostroke engines have beenproposed with scavenging ports at the middle of the cylinders andexhaust valves at the cylinder ends, but as far as we know theseconstructions have not hitherto been carried into practice on account ofdifficulties as regards the cylinder design and especially theconstruction of the cylinder end through which the piston rod passes. Inaccordance with one of the earlier proposals an exhaust valve was to bemounted in this cylinder end so as to surround the piston rod, but sucha construction is inapplicable in practice because the valve gets veryheavy and demands far too large forces for being actuated, and likewiseit is impossible to overhaul it without a very large work ofdisassembling.

In accordance with another proposal it has been attempted to avoid thesedifficulties by mounting the exhaust valve of the bottom end in aspecial way in the cylinder cover, i. e. to the side of the passagemeans for the piston rod and directed obliquely in relation to thelatter. This construction, however, in part suffers from the drawbackthat thescavenging of the bottom end will not get very effective onaccount of the unilateral exhaust and the central piston rod, in part itentails on accountof the unsym metrical construction, thedisadvantageous properties of which are further intensified by theexhaust valve getting comparatively large, a so unequal load on thecylinder cover and the liner on account of the combustion pressure andthe heat stresses that the construction must be considered inapplicable.

The purpose of the present invention is to construct a double-actingtwo-stroke engine with longitudinal scavenging in both cylinder ends, inwhich the advantages of the said known engine types are combined, Whiletheir drawbacks are avoided, so that an engine type is obtained which issuited for stationary engines and engines for vessels for large and verylarge outputs per cylinder unit, and which offers a combinationexpedient for practical purposes of slight weight and small requirementsas to space per efiect unit, simplicity as to construction, good loadconditions with regard to combustion pressures and heat stresses,besides reliability and easy access forinspection and dismounting.

The engine in accordance with the invention is of the kind which haslongitudinal scavenging of both cylinder ends through pistoncontrolledscavenging ports in a scavengin port section serving as central part inthe cylinder and poppet valve controlled exhaust openings in bothcylinder ends, of which ends the cylinder top has only a singlecentrally mounted exhaust valve, and the invention is characterized inthat the bottom end of the cylinder-i. e. the cylinder end through whichthe piston rod passeshas two obliquely mounted exhaust valves placedsymmetrically in relation to the piston rod passage means, and in thateach of the two cylinder ends consists af a bell-shaped body of steelmade in one piece, which body is by a heavy clamping flange .at the openend clamped to the central part, and which at some distance outside theclosed end has a light, preferably substantially plate-shaped collar,through which the passage means for exhaust valves, fuel valves,starting valves, etc. and piston rod stufiing box are carried into theclosed cylinder end, which collar along its outer edge bears against andforms the termination of a coolin jacket enclosing the said cylinderend, while in a way known per se the central part forms a longitudinalgirder serving as scavenging air box, which girder transmits thecombustion forces to the remaining parts of the framing and from whichthe cylinder ends project so as to be able to expand freely upwards anddownwards.

By this construction a scavenging in the bottom end may be attainedwhich is just as effective as the scavenging in the top end, and alldifliculties in making especially the bottom cylinder able to withstandcombustion pressures and heat stresses are eliminated. The fact is thatthe closed, bell-shaped cylinders made in one piece are in themselvesvery strong, and the symmetrical mounting of the exhaust valves at theclosed end of the bottom cylinder ensures an even and uniform heating ofthe latter, and likewise there will be room enough for arranging coolingspaces. By separate cylinder covers being dispensed with, the usual veryheavy clamping means for the latter are also omitted, and the combustionpressures are transmitted direct through the cylinders to the centralpart and from there to the stationary framing without the cylindersbeing prevented from expanding longitudinally.

The outwards-facing ends of the cooling jackets are, as mentionedbefore, formed by light collars on the cylinders, and these cannot giverise to perceptible heat stresses, as they may be made thin andyieldable. Correspondingly the inwardsfacing ends of the cooling jacketsmay in accordance with the invention bear on light collars which arecast in one piece with the cylinders and are situated in the vicinity ofthe clamping flanges of the latter. The cooling jacket proper may thenconsist of a simple cylindrical tube which is clamped to one collar andhas a movable sealing against the edge of the other collar.

In double-acting internal combustion engines it is known to provide therunning surfaces of the cylinders with a tripartite liner of a materialwith good running properties, such as cast iron. This known measure mayin the engine in accordance with the invention be taken in an especiallyadvantageous way, the composite wearing liner consisting of two simplecylindrical liners of a very slight thickness of material, which arepressed or shrunk each into its own of the bellshaped steel cylinders,While the central liner part situated in the scavenging air box is of aconsiderable thickness of material and along the whole of itscircumference is provided with evenly distributed scavenging air ports.By this arrangement is attained that the two liner parts which aresubjected to wear get short and thin and of a very simple construction,so that they can be given the proper uniform hardness conditioning aslight wear, and also may be replaced without high costs and without itbeing necessary to change the central liner part. This may therefore begiven a thickness of material that is sufficently large for attaining agood control of the scavenging air, and the expensive work done at themilling out of the scavenging ports is not wasted at the replacement ofthe wearing liners.

While the control of the exhaust valve of the top cylinder does not giverise to diliiculties, it is not possible without further ado to controlthe two exhaust valves of the be torn cylinder from the same cam shaftbecause these valves are mounted one on each side of the piston rod, andhave their valve spindles pointing obliquely outwards and downwards indifferent directions. The invention also comprises an especiallysuitable actuating mechanism for the exhaust valves of the bottomcylinder, which mechanism is characterized in that a push rod actuatedby a cam disk mutual to both valves is led down into the closed crankcase of the engine and from there actuates the valve spindles throughvertical push rods which project upwards from the crank case,

each one under its valve spindle, and actuate the latter throughapproximately hammer-shaped rocking levers.

In an expedient embodiment of this actuating mechanism the pressure rodsand levers situated in the crank case have only loose pressureconnections which will need no lubrication except the oil splash in thecrank case.

The invention is illustrated on the accompanying drawing by anembodiment.

Fig. 1 shows a vertical cross section through an engine in accordancewith the invention, in part diagrammatically, and

Fig. 2 what is shown in Fig. I viewed from the right in part from theoutside and in part in section.

On the drawing, which must be supposed to show a single cylinder unit ina multi-cylinder engine, I designates a central part of a cylinder, towhich a top cylinder 2 and a bottom cylinder 3 are bolted by means ofheavy clamping flanges 5 and 6 respectively. The central part I togetherwith the central parts of the adjacent cylinder units form alongitudinal girder, from which the top and bottom cylinders project soas to be able to expand freely upwards and downwards respectively, andwhich by means of bolts and nuts 3| is secured to frames 4 mountedtransversely to the longitudinal direction of the engine, through whichframes the combustion pressures are transmitted to the remaining partsof the stationary engine framing which is not shown on the drawing.

The top and the bottom cylinders 2 and 3 are made as heavy bell-shapedbodies of evolution of steel and both have at their outermost end arather large central passage means for an exhaust value l3' and for thepiston rod l6 respectively. These passage means have the form ofcomparatively heavy tubes co-axial with the bell-shaped cylinder bodies,and they carry at their outwards-facing ends light, substantiallyplate-shaped collars l and B respectively, the outer diameter of whichis somewhat larger than the outer diameter of the cylinder bodies. Thecollars and 8 are machined on their outer edges and form cylindricalbearing surfaces for tubular cooling jackets 9 and [0 respectively.These are bolted to corresponding light collars H and I2 at theinwards-facing ends of the cylinders.

Through the collars 1 and 8 passage means are carried for the usualcylinder fittings, such as fuel valves, starting air valves, indicatorvalves, safety valves, etc. These passage means consist of light tubeswhich are cast in one piece with the cylinder bodies and the collars andthe thickness of material of which is chosen so that they cannot giverise to heat stresses. A single pas sage means of that kind is shown byI! in Fig. l. The bottom cylinder furthermore contains two correspondingpassage means for exhaust valves [4 which are mounted symmetrically inrelation to the piston rod and directed obliquely in relation to theaxis of the latter. By this mounting of the exhaust valves it getspossible to obtain a sufficiently large exhaust area without thecombustion space getting any detrimental pockets.

. The exhaust valve l3 of the top cylinder is'controlled in the usualway from a cam shaft l8 by means of a push rod I 9 and a rocker arm 20.The exhaust valves of the bottom cylinder are controlled from the samecam shaft through a push rod 2| which is led down into the closed crankcase 30 of the engine, where it actuates a bell crank 23 which isrotatable around a stationary spindle 22. The other arm of the said bellcrank through a rod 24 actuates another bell crank 25 which is securedto a spindle 26 which is journalled in the crank case and furthermorecarries a lever of the second order 25'. This and the other arm of thebell crank 25 actuate vertical push rods 21 which through guides 29 arecarried up through the upper wall of the crank case directly below thefreely projecting ends of the valve spindles, on which they act throughhammer-shaped rocking levers 28 that are pivotal around stationary pins.The whole actuating mechanism thus contains only loose pressureconnections and need no other lubrication than the oil splash in thecrank case. Most of the actuating mechanism lies hidden in the crankcase and thus does not prevent access to the downwards-facing end of thebottom cylinder and to the stufiing boxes l5 and 36 of the piston rod.

The running surface of the assembled cylinder is formed by cast ironliners, i. e. one liner part 32 inserted in the central part I and twoliner parts 34 and 35 inserted in each cylinder body. The central linerpart '32 is made rather heavy so that the scavenge ports 33 milled outin its material become long enough to efiect a good control of thescavenge air. The outer liner parts 34 and 35 are on the other handquite thin and are quite concealed in the cylinder bodies, in which theyare secured by pressing or shrinking. They may, as shown, have a smalledgefor fixing their position at the insertion but ar otherwise made ofa mainly uniform thickness of material and without heavy flanges. Theyare therefore cheap to replace, while the central liner part 32 need notbe replaced as it does not get perceptibly worn.

The invention is not bound to the embodiment shown and described, thedetails of which may be varied in difierent ways. By way of example thecooling jackets of the cylinder bodies may be constructed in other waysthan that shown, if only the light collar mounted on the cylinder bodyis preserved as a termination of the cooling space. The valves may becontrolled in other ways than that shown by mechanical, hydraulical, orpneumatical means. The central part of the cylinder may form a coherentgirder for several cylinders or may consist of single pieces, bolted orwelded together, if so desired and construction of the framing may beanother than that shown.

I claim:

1. Double-acting upright two-stroke internal combustion engine havingpiston-controlled scavenging ports provided in a, central cylindermember, bell-like top and bottom cylinder members bolted to said centralcylinder member and projecting freely upwards and downwardsrespectively, exhaust valve means in the upper end of the top cylindermember and two exhaust valves of the poppet valve type mounted in thelower end of the bottom cylinder member symmetrically with respect tothe piston rod and with their valve stems directed downwards andoutwards to either side, light plate-like flanges integral with theouter ends of the top and bottom cylinder members and situated a shortdistance above and below the same respectively. separate cooling jacketsenclosing the projecting portions of the top and bottom cylinder membersand joined fluid-tight to either of said flanges along the peripherythereof, apertures for exhaust valves and remaining cylinder accessoriesbeing provided through each of said flanges and end of correspondingbell-like cylinder member.

2. Double-acting two-stroke internal combustion engine as claimed inclaim 1 having light flange-like collars integral with and situated inthe vicinity of the inner end of top and bottom cylinder membersrespectively and completing the cooling jacket of each.

3. Double-acting two-stroke internal combustion engine havingpiston-controlled scavenging ports provided in a central cylindermember, bell-- like top and bottom cylinder members bolted to saidcentral cylinder member and projecting freely upwards and downwardsrespectively, exhaust valve means in the upper end of the top cylindermember and two exhaust valves of the poppet valve type mounted in thelower end of the bottom cylinder member symmetrically with respect tothe piston rod and with their valve stems directed downwards andoutwards to either side, light plate-like flanges integral with theouter ends of the top and bottom cylinder members and situated a shortdistance above and below the same respectively, separate cooling jacketsenclosing the projecting portions of the top and bottom cylinder membersand joined fluid-tight to either of said flanges along the peripherythereof, apertures for exhaust valves and remaining cylinder accessoriesbeing provided through each of said flanges and end of correspondingbell-like cylinder member, a camshaft with a cam operating a push rod, asystem of levers and rods enclosed in the crank case and actuated bysaid push-rod, and terminating with two push-rods projectingsubstantially vertically from the crank case in the immediate vicinityof the lower ends of said valve stems, pivoted hammer-like levers beinginterposed between the upper ends of said push-rods and the lower endsof said valve-stems.

MARK FERDINAND MEINERTZ.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 16,909 West Mar. 20, 1928905,598 Sohnlein Dec. 1, 1908 1,072,366 Sargent Sept. 2, 1913 1,540,286Roberts June 2, 1925 1,627,549 Becker May 10, 1927 1,674,832 Lugt June26, 1928 2,254,410 Andresen Sept. 2, 1941

